An organic electric device refers to a diode capable of inducing the flow of charges between an electrode and an organic material using holes and/or electrons. According to an operation principle, the organic electric device may be an electronic device in a type in which exitons formed in an organic material layer are divided into electrons and holes by a photon input from an external light source to a diode, and each of the divided electrons and holes is transferred to a different electrode and used as a current source; or an electronic device in a type which is operated by holes and/or electrons injected to an organic material by applying a voltage or current to at least two electrodes. An example of the organic electric device is an organic light emitting diode (OLED), an organic solar cell, an organic photo conductor (OPC) drum or an organic transistor.
The organic light emitting diode refers to a self-emissive diode using an electroluminescent phenomenon in which light is emitted when a current flows in an emissive organic compound. The organic light emitting diode is receiving attention as a next generation material in various fields of industry such as displays, lightings, etc. because of excellent thermal stability and a low driving voltage. However, in an operation of passing light generated in the diode through a stacked structure thereof, total reflection occurs, which decreases internal light extraction efficiency of the diode. Research on increasing in internal light extraction efficiency is being continued.
For example, in Korean Patent Application No. 2008-0122603, a diode deposited on an uneven surface formed by beads is disclosed. However, when an organic material is deposited on the uneven surface, a thickness probably becomes non-uniform, and thus the diode may be electrically unstable.
In Japanese Patent Application No. 2008-299250, scattering of light at an interface between a substrate and a high refractive material by planarizing unevenness formed on a substrate using the high refractive material is disclosed. However, a specific method of evenly forming the high refractive material on the substrate is not disclosed. To form a material layer having a refractive index of 1.8 or more, a method of depositing a high refractive material or a wet-coating a solution in which the high refractive material is dispersed is generally used. When wet coating is performed on an uneven surface, in the beginning of the coating, a coated surface is planarized, but as a solvent evaporates, the surface becomes uneven like the coated surface. Accordingly, when the coating is performed to a thickness at least two times a depth of unevenness larger than a thickness of the dried high refractive layer, a wave-shaped surface is possibly formed. Particularly, since a high refractive planarized surface has a low transmission degree and poor mechanical properties of the coating layer, it is increased in loss of light and decreased in physical strength as a thickness of the planarized surface is increased. As another method, although a method of thickly coating a high refractive inorganic material by deposition and then polishing the resulting layer may be used, it is very disadvantageous in mass-productivity and production cost.
In addition, in U.S. Patent Application No. 2009-365349, a method of preparing a substrate itself using a high refractive material, forming unevenness on one surface of the substrate by sanding and forming a diode on the other surface, which is planarized, is disclosed. However, the substrate manufactured using the high refractive material is very expensive, and the high refractive substrate is degraded in mechanical properties.